Pulleys



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United States Patent O 3,264,891 PULLEYS .Iiri J. Hovorlra, North Miami Beach, Fla., assigner to International Rotary Machinery Corp., Miami, Fla., a corporation of Florida Filed Feb. I8, 1964, Ser. No. 345,644 3 Claims. (Qi. 'M -230.17)

This invention pertains to improvements in automatically adjustable pulleys of the type which include relatively movable portions, and are intended to maintain uniform tension and minimize slippage between the pulley and the belt connected thereto, an example of such devices being that shown in my prior U.S. Patent No. 2,938,395. More specifically, the pnesenit invention relates to the provision of automatic take-up pulley means adapted to minimize belt slippage by utilizing the transmitted force in the belt to maintain a belt tension corresponding to the transmitted force.

It is a basic objective of the present invention to provide pulley assemblies wherein the tension on the belt is variably automatically responsive to forces applied to the belt to minimize belt slippage. A related object is to provide variance as indicated which compensates for wear and elasticity in the belt to maintain substantially constant tension.

Another object is to supply a constant tension pulley system which, through maintenance of constant tension, reduces wear on related components such as bearings and the like. Bearing life is extended due to regulation of belt tension in accordance with the load transmitted by the belt, thereby loading the bearing only to that extent necessary to transmit the required load.

Still another object is to provide a pulley-belt arrangement which minimizes frictional losses and transmits substantially full power from a drivingto a driven component.

A further object is to supply a belt and pulley system which eliminates the need for belt slack take-up mechanisms and periodic center-to-center adjustments which are customarily used to compensate for belt stretch and wear. A related advantage is increased belt life due to constant tensioning and elimination of slippage.

Other and further objects and advantages of this invention will become apparent to those skilled in the art from a consideration of the following specification when read in conjunction with the annexed drawings, in which:

FIGURE 1 is a longitudinal cross sectional View taken substantially centrally through a first form of pulley constructed and assembled in accordance with the teachings of this invention;

FIGURE 2 is a vertical cross sectional View of the pulley, taken on the Isection yli-ne 2--2 of FIGURE l, looking in the direction of the arrows;

FIGURE 3 is a disassembled longitudinal sectional view;

FIGURE 4 is an enlarged end view of a cam follower element hereof;

FIGURE 5 is a fragmentary side elevational view of the follower of FIGURE 4;

FIGURE 6 is a fragmentary perspective View, partially in cross section, of adjacent pulley Walls hereof;

FIGURE 7 is a representation of an expression of the equilibrium of the Walls and belt in stable, operating condition;

FIGURE 8 is a view similar to FIGURE 1, showing a second form of the invention;

FIGURE 9 is a vertical cross sectional View, taken substantially on the line 9-9 of FIGURE 8, looking in the direction of the arrows;

FIGURE 10 is a disassembled longitudinal sectional View of the modification shown in FIGURE 8;

FIGURE 11 is a detail sectional View taken substantially on the line lI-Il of FIGURE ll, looking in the direction of the arrows;

FIGURE l2 is a fragmentary, disassembled perspective View of the pulley of FIGURES 8-11; and

FIGURE 13 comprises perspective views from the front and rear of a retainer clip used in the modified form of the invention.

Referring to the invention in more to FIGURES l-S, illustrated therein 20 of this invention. The assembly 20 includes a first, fixed sheave means 22 comprising an inner sleeve 24 of tubular form with a bore 26 therein and having inner and outer ends 28, 30. The bore 26 has a smooth section 32 adjacent the end 28, and a threaded section 34 extending inwardly from the outer end 30. The sleeve 24 includes an outer wall 36.

An interchangeable bushing 33, having a threaded outer side 40 engaging the threaded section 34, whereby the sleeve is mounted thereon, is provided, and the bushing has an axial bore 42 which receives a drive shaft or the like (not shown). The bushings 38 are supplied with bores 42 of various sizes to accommodate shafts of varying diameters. As seen in FIGURES 1 and 3 the sleeve 24 and bushing 38 have co-aligned, threaded openings 44, 46 therein to receive a setscrew 48, thus locking the bushing and sleeve to one another and to the shaft.

Intermediate the ends 28 and 30 of the sleeve 24, a first pulley wall 50 extends outwardly from the outer wall 36. At least the inner side 5l of the rst pulley Wall 50 is outwardly inclined and extends peripherally about the sleeve 24, and terminates in a horizontal flange 52. At spaced locations, radially extended, integral gussets or support ribs 54 for the wall 50 are supplied.

The pulley assembly 20 further includes a second, movable sheave means 56 comprising a tubular outer sleeve 58 with a closed distal end 60 and an open proximal end 62, the sleeve having a bore 64 and an outer wall 66. As shown in the drawing, the outer sleeve 58 is slidably and rotatably mounted on the inner sleeve 24, the latter being received in the open proximal end 62 of the outer sleeve. The end 60 of the sleeve 58 is closed by an end wall 63 which has a centrally located, substantially cylindrical, cupped follower support extended inwardly therefrom. The follower support terminates in an inner wall 72 having a diametric bore 73 formed therein, the purpose of which appears in more detail below.

Closely adjacent the end 62 of the outer sleeve S8 and extending from the outer wall 66 thereof is a second pulley wall 74 with an inclined inner side 76, and reinforced by radially arranged gussets or ribs 78 and having a rearward peripheral flange 80.

Inward and outward relative adjustment between the rst and second sheaves occurs through movement of the movable second sheave relative to the first, fixed sheave. Such movement is directed and controlled by cam means detail, and initially is a pulley assembly secured to the respective sleeves and including a follower bearing 82 of elongated, substantially cylindrical form mounted in the bore 73 of the support wall 72 and having ends 84, 86 extended outwardly therefrom. As best seen in FIGURES 4 and 5, the ends 84 and 86 each have peripheral grooves 88 formed thereabout. As seen in FIG- URES l and 3, the sleeve 58 has an opening 90 therein to permit insertion of the follower bearing therethrough and into the bore 73. In such location, snap rings 92 are installed in grooves 88 thereby to secure the follower in place.

Fixedly secured to the smooth outer section 32 of the bore 26 of the inner sleeve 24 at the end 28 thereof are a pair of spaced apart cam elements 94 mounted opposite one another. The elements 94 each have inward cam surfaces 96 engaged by the follower ends 84, 86, the cam surfaces including a central area 98 of maximum distance from the end 28 and declining sides 100 curved outwardly.

Referring now to the modified embodiment of FIG- URES 8-12, an arrangement quite similar to the rst described form of the invention is shown, like elements being identified by the same numerals employed in the rst described form in the drawing, With a letter a appended thereto for distinction. Basic distinctions between the pulley assemblies 20 and 20a concern the cam means employed in each. In the assembly 20a, the bore 26a of the inner sleeve 24a is enlarged at 200 adjacent the end 28a to receive a cam spring retainer 202 having an annular side wall 204. As seen in FIGURE 8, the sleeve 24a has threaded openings 206 therein aligned with corresponding openings 208 in the retainer wall 204 and setscrews 210 are extended through the openings to secure the retainer in place. The retainer further includes spaced apart forward walls 212 with open areas 214 therebetween (FIGURE 13), and rearward, diametrically opposite clips 216 form the rear walls of the retainer. Cam springs 218, identical but oppositely arranged, are provided, and have outer ends 220 secured to the retainer forward walls adjacent open areas 214. As best seen in FIGURE 11, the pairs of open areas 214 and pairs of clips 216 are longitudinally aligned with respect to one another, and hence, the springs 218 have opposite maximum depth areas 222 at their connections with the clips 216, and opposite minimum depth areas 224.`

The follower support 70a on the end wall 68a of the outer sleeve 58a of the second form of the invention has integral, outward follower elements 226 and 228, each of which includes a rounded bearing side surface 230 engaging the cam springs 218 as shown in FIGURE 8.

FIGURES 6 and 7 relate to each form of the invention and disclose the manner of operation thereof. As shown in the former, a belt 300 with opposite declining sides 302, 304 is positioned between the xed and movable sheaves frictionally contacting the faces 76 and 51 (or 76a and 51a), respectively, thereof. The belt transmits radial force F applied thereto into frictional forces Ff between the belt and sheaves, which in turn causes the movable sheave to rotate with the belt relative to the fixed sheave. This relative rotation of the movable sheave causes the cam follower means 84, 86 or 226, 228 to move along the inclined planes of the cams 94 or 218, and consequently produces axial, twisting movement of the movable sheave relative to the xed sheave. The movement continues until the frictional force between the sheaves and belt equals the force in the belt, at which point the pitch diameter of the pulley has reached a point where no slippage occurs. When used as a driver the fixed sheave will rotate relative to the movable sheave until the frictional forces and the tensile force are equal. When used as a driven element, the movable sheave will rotate with the belt relative to the xed sheave, again until the frictional forces equal the tensile force.

Otherwise expressed, as in FIGURE 7, equilibrium is established at:

where T=Belt tension F :Radial force F f=Frictional force between belt and sheave N :Normal force between belt and sheave MbS=Coeflicient of friction between belt and sheave The pulley system described above automatically eliminates belt slippage by utilizing the transmitted load in the belt to maintain a belt tension corresponding thereto. Thus, removal of belt slippage as a factor in a drive system indicates that substantially full horsepower, minus frictional losses can be transmitted from a driving to a driven component.

Having described and illustrated two forms of this invention in some detail, it will be understood that these descriptions and illustrations are offered merely by way of example, and that the invention is to be limited in scope only by the appended claims.

What is claimed is:

1. A self-tensioning pulley assembly mounted on a rotatable shaft, for use with a belt of substantially V-shaped cross section, the pulley assembly comprising:

substantially cylindrical, externally threaded bushing means, fixed about the shaft;

tubular inner sleeve means with opposite ends, having a bore formed therein and extending therethrough with a threaded section and a smooth section, threadedly connected at the threaded section to the bushing means and rotatable therewith in xed relation to the shaft;

an inclined rst pulley Wall, including inner and outer sides, xedly secured to the sleeve means intermediate the ends thereof with a portion of the sleeve outer wall extended forwardly thereof;

spaced apart, radially extended support ribs extending between the wall outer side and the sleeve means;

tubular outer sleeve means journaled on the forwardly extended portion for forward and rearward sliding movement and having inner and outer ends;

an end wall xed to the outer end of the outer sleeve means;

an upstanding second pulley wall fixed to the outer sleeve adjacent its inner end, the second pulley wall being oppositely inclined with respect to the first pulley wall;

spaced apart, radially extended support ribs extending between the second pulley wall and the outer sleeve means; and

cam means secured to the end wall of the outer sleeve means and extended inwardly thereof and secured to the smooth section of the inner sleeve means causing inward and outward movement of the outer sleeve means relative to the inner sleeve in response to changes in belt tension.

2. The invention of claim 1 wherein the cam means comprises:

a substantially cylindrical, inwardly extended follower support secured to the end wall of the outer sleeve, having a substantially diametric opening formed therein;

an elongated cam follower bearing mounted in the opening of the follower support and having end portions extended outwardly thereof;

a pair of oppositely mounted cam elements, secured to the inner sleeve of the smooth section of the bore therein adjacent the inner end of the inner sleeve;

each of the cam elements having inner cam surfaces en- .Y gaged, respectively, by the bearing means of the fol lower; and

each of the cam surfaces including a central area extended inwardly of the inner sleeve and outwardly curved side portions.

References Cited by the Examiner UNITED STATES PATENTS Jereb 74-23024 Hovorka. Getz et al. Pauli 74--230L24 X DAVID I. WILLIAMOWSKY, Primary Examiner. 10 L. H. GERIN, Assistant Examiner. 

1. A SELF-TENSIONING PULLEY ASSEMBLY MOUNTED ON A ROTATABLE SHAFT, FOR USE WITH A BELT OF SUBSTANTIALLY V-SHAPED CROSS SECTION, THE PULLEY ASSEMBLY COMPRISING: SUBSTANTIALLY CYLINDRICAL, EXTERNALLY THREADED BUSHING MEANS, FIXED ABOUT THE SHAFT; TUBULAR INNER SLEEVE MEANS WITH OPPOSITE ENDS, HAVING A BORE FORMED THEREIN AND EXTENDING THERETHROUGH WITH A THREADED SECTION AND A SMOOTH SECTION, THREADEDLY CONNECTED AT THE THREADED SECTION TO THE BUSHING MEANS AND ROTATABLE THEREWITH IN FIXED RELATION TO THE SHAFT; AN INCLINED FIRST PULLEY WALL, INCLUDING INNER AND OUTER SIDES, FIXEDLY SECURED TO THE SLEEVE MEANS INTERMEDIATE THE ENDS THEREOF WITH A PORTION OF THE SLEEVE OUTER WALL EXTENDED FORWARDLY THEREOF; SPACED APART, RADIALLY EXTENDED SUPPORT RIBS EXTENDING BETWEEN THE WALL OUTER SIDE AND THE SLEEVE MEANS; TUBULAR OUTER SLEEVE MEANS JOURNALED ON THE FORWARDLY EXTENDED PORTION FOR FORWARD AND REARWARD SLIDING MOVEMENT AND HAVING INNER AND OUTER ENDS; AN END WALL FIXED TO THE OUTER END OF THE OUTER SLEEVE MEANS; 